The present proposals have to do with hand-operated dispenser pumps, and partially in certain aspects to such pumps adapted for the dispensing of foam from a supply of foamable liquid in a container to which the dispenser is fitted.
Over the last 15 years or so the use of foam dispensers based on aerosols using pressurized gas has declined steeply for environmental reasons, leading the development of foaming dispensers which exploit a manual pumping action to blend air and liquid and create foam.
A particular category of such known dispensers to which certain of the present proposals relate (referred to in what follows as foaming dispensers xe2x80x9cof the kind describedxe2x80x9d) provides both a liquid pump and an air pump mounted at the top of a container for the foamable liquid. The liquid pump has a liquid pump chamber defined between a liquid cylinder and a liquid piston, and the air pump has an air pump chamber defined between an air cylinder and an air piston. Preferably these components are arranged concentrically around a plunger axis of the pump. The liquid piston and air piston are reciprocable together in their respective cylinders by the action of a pump plunger: typically the two pistons are integrated with the plunger. An air inlet valve and a liquid inlet valve are provided for the air chamber and liquid chamber. An air discharge passage and a liquid discharge passage lead from the respective chambers to an outlet passage by way of a permeable foam-generating element, preferably one or more mesh layers, through which the air and liquid pass as a mixture. Preferably the air discharge passage and liquid discharge passage meet in a mixing chamber or mixing region immediately upstream of the permeable foam-generating element.
It is not easy to achieve a good quality foam consistently from dispensers of the kind described. There are also difficulties in providing for adequate venting and valving of the different fluid spaces and paths while assuring a positive operation without leaks.
EP-A-565713 (equivalent to U.S. Pat. No. 5,271,530) describes admitting air to the air cylinder through a ball valve in the top wall of the air piston. This does not work when wet, nor when the plunger is pressed slowly, and there is a problem of liquid entering the air chamber via the mixing chamber and air discharge passage.
EP-A-613728 refines the air valving using a single elastomeric annulus in the air piston roof whose outer rim acts as an air inlet flap valve and whose inner rim acts as an air discharge flap valve against the plunger stem. This arrangement dispenses air at all speeds and helps prevent liquid getting into the air chamber.
WO-A-97/13585 notes a tendency for such a double-acting valve element to stick, and addresses this by providing some axial play between the plunger stem and the air piston. This play is taken up in alternating directions as the plunger reciprocates, keeping the valve element moving freely.
EP-A-736462 is another system using axial lost motion between air piston and plunger, for a double-acting valve action via holes near the inner periphery of the air piston roof.
Our present proposals provide new and useful developments in various aspects of the construction of dispensers, particularly foam dispensers of the kind described. A first set of aspects is concerned with the venting and valving of air flows in relation to the air chamber. A further aspect relates to venting in plunger operated pumps in general. Other aspects relate to a new overall disposition of the pump parts.
A first proposal herein is that the plunger includes a cap shroud whose outer skirt continues down and connects fixedly or integrally adjacent the air piston""s peripheral seal, defining thereby an internal cap air chamber above a roof of the air piston, enclosing the air inlet valve. Access for exterior air to the air chamber in the air cylinder is then via this internal cap air chamber. External air may enter the cap through one or more holes in the cap shroud e.g. holes above where the cap shroud projects through a guide opening of a fixed pump body.
A further independent but combinable proposal herein is that the air inlet valve through which air enters the air chamber comprises a radially inwardly-projecting flexible valve flap formed integrally with at least an outer sleeve portion of the air piston, carrying or including a seal portion shaped to engage the air cylinder wall. In a preferred embodiment this outer sleeve of the air piston is fixed directly to a cap shroud of the plunger which encloses the air inlet.
The air inlet valve flap, which preferably extends substantially in a radial plane and is preferably a uniform annulus, is flexible relative to an air inlet valve seat. A preferred valve seat is a downwardly-directed edge, especially an annular edge, of a core sleeve comprised in the pump plunger and which moves axially, preferably fixedly, with the pump plunger.
Desirably the components of the pump plunger are fixed together in pre-determined axial register so that the air inlet valve flap is resiliently urged axially against the air inlet valve seat, such as the annular edge of a core sleeve as mentioned. The air discharge passage may lead up inside such a core sleeve. The core sleeve may then also provide a valve seat for air outlet valve flap which is provided on a radially inner plunger core portion. Or, the core sleeve may itself comprise integrally an air outlet valve flap e.g. extending from at or from adjacent the seat edge engaged by the inlet valve flap. Thus, in one preferred embodiment the air inlet valve flap extends radially relative to, e.g. inwardly of, the core sleeve, and an air outlet valve flap extends radially (or at least, with a radial component) out towards or in from the core sleeve. Such a core sleeve preferably encloses an annular air discharge space, all or partly downstream of the air outlet valve when one is provided, and communicating (from downstream of any such outlet valve) inwardly (optionally also upwardly) to a mixing chamber for liquid and air. Such a mixing chamber and/or the point(s) of air injection into such a mixing chamber is preferably axially overlapped by the annular air discharge space in the core sleeve. This gives an axially compact construction.
The core sleeve in any of the other embodiments may be constituted by a downward skirt from a plunger component. This skirt may include a core part projecting down inside the core sleeve at a radial spacing. This inner core part might be for example a surround to a mixing chamber, through which the air is injected, and/or part of a plunger stem which is or carries the liquid piston.
A further proposal herein is that the air outlet valve is provided as an upwardly diverging conical or cup-shaped element, sealing outwardly against an inwardly directed air discharge passage wall, such as that of a core sleeve as mentioned above, or some other part of the air discharge passage. A benefit of this air outlet valve conformation is that it catches drops of liquid escaping from the foam-generating region and helps prevent them from reaching the air chamber.
Further aspects herein relate to modes for arranging the mixing of liquid and air. Typically the liquid discharge passage rises axially from the liquid chamber in the liquid cylinder. The liquid discharge passage may extend up inside a hollow stem inside the plunger. A liquid discharge valve is usually provided for this passage. We prefer to provide the valve at the entrance to the passage e.g. by means of a sliding seal on the liquid piston which covers and uncovers windows in the hollow stem However, it would also be possible to provide a liquid discharge valve midway along the liquid discharge passage, as in the prior art patents mentioned above. Preferably a mixing chamber or region where air and liquid are present together is provided immediately upstream of the foam-generation element. We prefer that at or immediately before this mixing chamber the liquid discharge passage diverges around a central baffle or block, either freely in a chamber or along one or more restricted diametrically-spaced passageways in parallel. The airflow from the air discharge passage may impinge on this diverged or distributed liquid flow in order to promote mixing.
We prefer that the air discharge passage opens to the region of mixing with the liquid, e.g. into a mixing chamber, with a substantial radially inward direction component. Optionally, it may also have a tangential component. We particularly prefer that the air discharge passage has a circumferentially distributed air injection locus e.g. surrounding or opposed across the liquid flow. There may be plural (for example at least two or at least three) air injection points at the combination with the liquid flow. The liquid flow may rise as a generally tubular curtain from a generally annular slit forming an outlet of the liquid discharge passage.
The preferred foam-generating element uses one or more layers of mesh to produce a uniform foam for discharge. The nature of the mesh is not critical: we prefer a coarser mesh followed by finer mesh. These meshes may be provided on a foam-generating module in which discs of the meshes are bonded across the open ends of a short tube which can be fitted into a complementary housing recess of the plunger during assembly.
A third aspect of the present proposals relates to a novel disposition of the discharge passageways. In this aspect the pump has a fixed discharge nozzle arrangement beside the reciprocable plunger. The air and liquid discharge passages leave the respective chambers at or adjacent their bottoms, and the foam-generating element is fixed in or beneath the fixed nozzle component, instead of being in the plunger as in prior art designs. There is obvious user benefit in having a foaming dispenser whose discharge nozzle does not move during dispensing. The necessary topology of discharge passages can be created with injection-moulded components using a moulded discharge-passage forming lower shell which fixes on to the pump below the cylinder-forming component(s).
In all of the above aspects it is preferred that the air cylinder and liquid cylinder be concentric. It is also preferred, as in the prior art, that they are formed together in one piece of plastics material. The cylinder-forming component(s) can be secured into a container neck either directly, e.g. by having its own downturned rim with appropriate securements (thread or snap ribs), or indirectly by means of a discrete retaining collar having such securements.
A further aspect may relate to the first proposal above, i.e. venting for the air cylinder of a foam dispenser via the cap shroud, but is also independently applicable in general in pumps which have a pump body secured to the top of a product container, e.g. integrally or by means of a screw or snap cap, and the pump is operated by a plunger which works reciprocally in or on the pump body to alter the volume of a pump chamber communicating via an inlet valve with the container interior andxe2x80x94usually via an outlet valvexe2x80x94with a discharge opening. Usually the plunger carries a piston working in a cylinder provided by the body, although it can be the other way around. The discharge opening may be on the plunger (moveable nozzle pump) or on the body (fixed nozzle pump).
In any event there is a general need in dispenser pumps of this kind to allow air into the container or pump to compensate a volume dispensed.
One conventional product vent arrangement provides one or more small vent holes through the cylinder wall near the top. Air can enter the pump body through the clearance between the plunger stem and the surrounding collar of the body cap and into the container space via the vent holes, which are above the piston seal. In other known constructions the vent channel bypasses the cylinder interior e.g. by means of a channel between a closure cap and the container neck to the container interior, or a channel from the above-mentioned clearance around the stem which skirts around the top of the cylinder wall. A further possibility is to vent air inwardly through a hole or channel in the plunger head itself rather than through an annular clearance between plunger and collar.
While conventional venting relates to compensating for volume of dispensed product, there may be other needs for venting air. In particular, foam dispensing pumps as described herein are adapted to dispense foam by pumping simultaneous flows of air and liquid to some mixing location in the pump. In this case there is a need to admit air to the pump system for pumping to form foam, and the volume of air required is likely to be greater than the volume required for compensating dispensed liquid product volume. We particularly envisage use of the present proposals for air venting in such a foaming dispenser or in conjunction with other plunger-operated foam dispensers which pump air and liquid together in the manner referred to above.
Known foam dispensers admit air for pumping by various routes, including some of those mentioned above.
There are special difficulties when a dispenser has to be used in a wet environment, e.g. outdoors in the rain, or especially indoors in a shower. Water has a tendency to get in or be drawn in through the air vents, particularly where these are between the plunger stem and collar surround because water can lie in the gap. Water getting in this way can contaminate or dilute the product in the container. In a foam dispensing pump it can accumulate undesirably in the air pumping system.
What we propose in this aspect are new arrangements for venting air via an opening in the shroud or casing of a pump plunger, and particularly where the plunger (e.g. the mentioned shroud or casing thereof) makes a close or sealing fit through the collar or other top opening of the pump body so that venting there is prevented or is insufficient. What we propose is to provide a cover element overlying one or more vent opening(s) of the plunger casing. Preferably this cover element is a discrete second element which is clipped or snapped onto or into a first element of the plunger casing. Access to the opening(s) through the plunger casing is or is via a venting clearance defined between the cover element and the plunger casing. Entry to this access clearance may be via one or more entry openings defined on one side by the edge of the cover element.
The opposed surfaces of the casing and cover element may define between them one or more elongate and/or tortuous channels or clearances leading from the entry opening(s) to the opening(s) which open(s) to the interior of the casing. To provide elongate and/or tortuous channels or clearances, the surface of a discrete cover element and/or of a first plunger casing element can be formed with grooves or open channels or other recesses which become closed channels or clearances when the cover element and plunger are assembled together. When they are discrete components, it is simple to form non-straight (bent or curved) channel or clearance shapes by moulding.
It is strongly preferred that from the entry opening(s) the access path between the cover element and plunger casing leading to the opening(s) through the casing is at least partly uphill. The path(s) may be for example uphill at least from the entry opening(s). Additionally or alternatively it is uphill over most or all of its length. This helps to drain away any water which may get into the venting clearance.
The cover element may be laminar. It may for example be a simple single layer with integral fasteners such as snap pins or pegs by which it is secured to the main plunger casing.
A particularly preferred position for the cover element is on top of or as the top of the plunger. It may extend to a lateral extremity of the plunger, e.g. to the side and/or a rear face, and have the entry opening(s) there to reduce the chance or water collecting at the vent. In a preferred embodiment the top of the plunger slopes down to the rear and the cover element provides or is on the sloping region, with one or more entry openings at the rear of the plunger below the rear edge of the cover element. One or more elongate and/or tortuous vent channels may be defined between a plunger top surface of a first element and the cover element. Such channel(s) might extend forwardly up that top surface, and one or more corresponding holes through the wall of the first element and into the plunger interior towards the front. In this embodiment the cover element may be presented as a finger grip push button finish for the plunger. It may be outwardly concave.
Or, the one or more vent channels may open to the plunger interior at an opening also defined between the cover element and the first plunger element. Indeed the whole channel may be defined between opposed surfaces of such elements, to take advantage of the ease of forming complicated internal moulded shapes between opposed surfaces of discrete components.
There are cosmetic advantages to providing the entry opening(s) between the plunger casing and the edge of the cover element, because the existence of the boundary distracts the eye from the opening. Nevertheless it is in principle possible to provide the entry opening through a first, inner element plunger casing only, and lead it to the interface between the casing and cover element, again to take advantage of the ease of making a more tortuousxe2x80x94and hence less water-penetrablexe2x80x94vent passage between two elements.
The present proposals are particularly useful where the plunger casing extends down as a continuous shroud into the pump body opening, particularly with a sealing fit. Such a shroud or cap may enclose an interior plunger cavity. We also envisage, where the plunger houses a hollow discharge channel of the pump leading to a nozzle, that the channel formation of one or more vent passages as mentioned above may extend alongside e.g. to either side of the discharge channel wall at the top of the plunger. From the interior of the plunger, the route for vented air is not particularly restricted. For example in a foam-generating dispenser it may pass down inside the plunger to an air intake valve for an air cylinder, which may be the only other opening from this interior space of the plunger.
A further embodiment has a plunger cap having an upwardly open, generally tubular lower element and the cover element as a top lid or closure which defines at least part of a discharge channel e.g. nozzle for the pump, at the same time as defining between it and the lower element a vent channel or vent channel entry according to any of the proposals previously outlined, when the elements are fitted together e.g. with the top lid plugging the lower element. The top lid may also provide a core sleeve or core sleeve portion as referred to previously, preferably as a one-piece integral downward extension.